Television-telephone system



April 1, 1941 A. N. GOLDSMITH- TELEVISION-TELEPHONE SYSTEM Filed Dec.27, 1937 3 Sheets-Sheet 2 Euwba Wm mm INVENTOR. I ALFRED N. GOLDSMITH 7I M ATTORNEY.

TESL Patented Apr. 1, 1941 water UNITED STATES PATENT OFFICETELEVISION-TELEPHONE SYSTEM Alfred N. Goldsmith, New York, N. Y.

Application December 27, 1937, Serial No. 181,853

Claims.

This invention relates to a television system and more particularly to atelevision system wherein telephone transmission constitutes a partthereof.

In the transmission of television image signals it has been customary totransmit with the television or video signals also audio signals which,

when reproduced with the video signals, provide an'observer with boththe sight and sound conditions obtaining at the point of transmission,However, up to the present time it has been practically a universalcustom to combine on the carrier frequency upon which the video signalsare transmitted all of the various signals or signal componentsappertaining thereto. Consequently,

' there have been transmitted along with the video The present inventionhas for its purpose that of providing a system for transmission of bothsound and picture signals and, in addition, the provision of a suitablearrangement by which the picture or video signals which are the mostdifficult to transmit, due to the wide frequency band required, forexample, will be grouped about a chosen carrier frequency, known as thevideo carrier and wherein the sound signals will be grouped about theaudio carrier and with these latter signals will be combined allauxiliary television indicia. It has already been established in the artthat while the sound transmission channel itself is very narrow, ascompared with the video channel, it, nevertheless, must be separated forcircuit and other reasons from the television channel by a relativelywide frequency band and this portion of the unused frequency band may beused conveniently and efficiently for the incorporation therein of allauxiliary television indicia.

Briefly, the present invention provides for a combinedtelevision-telephone transmission and reception system where there isseparate trans-v mission of the television signal (that is, thevideofrequency picture modulation alone or, insome instances, with someof its associated auxiliary picture-control signals) and thetransmission of the telephone signal in association with anyor all ofthe remaining picture-controlling signal.

Thus it is apparent that the picture-controlling signals, last referredto, include, for example, the line synchronizing signal and the linereturn blocking, the frame synchronizing signal and the line returnblocking and, in addition, the background control signal. In televisionsystems, as has already been proposed by Carlson in reissue Patent#20,?00 dated April 19, 1938, a fixed separation between the video andaudio carrier is maintained and in receiving the transmitted sig- I nalsit is customary in turning the receiver to tune to the sound signalwhereupon, because of the fixed separation, between the two transmittedcarriers, the video signal is also properly tuned. Reference herein ismade to the Carlson patent.

above'referred mm such portions thereof as are applicable to anunderstanding of this dis closure. Accordingly the present invention hasfor its primary object that of providing a television system Withaccompanying sound wherein the width of the sound and the picturefrequency bands shallbe more nearly equalized and the powerrequirementsmore evenly distributed, and wherein any interaction betweenthe television or video-modulation signal and the signals correspondingto the other television indicia will be minimized.

Other advantages and objects of this invention are to provide a systemfor transmitting both picture and sound signalswherein the stability ofoperation of the television receiver will be improved, as well as toprovide a simplification of.

the selective circuits by which the different signals are separated onefrom the other in the receiver in order to become efiective for thepurposes desired.

Still other objects and advantages will become apparent and at oncesuggest themselves to those skilled in the art by reading the followingspecification and claims in connection with the accompanylng drawingswherein Figure 1 is a schematic diagram of a combined television andsound transmission system;

Figure 2 is a schematic diagram of a receiver for receiving thetransmissions from the transmitterof Fig. 1;

FigureBis a schematic diagram indicating the relative .lband widths ofthe several different transmitted signals Figure 4 is a diagrammaticrepresentation closely analogous to that of Fig. 3; and

Figures 5 and 6 are expanded schematic diagrams of a portion of Fig. 4illustrating respectively systems wherein background signal is arrangedto modulate a sub-audible carrier which in turn modulates the soundcarrier and wherein the background signal modulates the sound carrierdirectly.

Referring now to the drawings for a further understanding of thisinvention the complete system has been shown in block diagram for thepurpose of simplification since each and every element thereof, exceptinsofar as these elements are combined one with the other and used incombination in a manner which, so far as is known, is new and novel inthe art, is known and has been used.

Briefly, a television system, as such is now customarily used in theUnited States and/or Great Britain comprises a camera or pick-up tubewhose output is fed to a video pre-amplifier from which the signal feedsinto a video amplifier and a mixer. In the mixer stage shading controlproduced from the shading adjustment generator, may be introduced. Theoutput from the video amplifier and the mixer is then fed to a videoamplifier and black-level control device into which is fed the output ofa suitable form of pedestal generator. This combined output is then fedto a video amplifier wherein are incorporated suitable means forintroducing the synchronizing signals which are produced from asynchronizing signal generator. The combined output of all of thesestages is then fed to a video amplifier and a modulator which is used tomodulate a suitable source of radio-frequency carrier energy. In thepick-up or camera end of the system the line and frame scanninggenerators are caused to control the scanning in substantially the samemanner as the control would be effective in the receiver. Likewise uponthe camera tube, if it is a storage type of device such as Zworykin hasdisclosed in many publications,

for example, a suitable blocked-out source of energy is applied to acontrol electrode to blank during return line periods. All of theblockingout generators, line scanning generators, the frame scanninggenerator, the pedestal generator and the synchronizing signal generatorare interlocked by a suitable form of timing arrangement. In order thatthe direct current component of the transmitted view may be introducedthis component is obtained at the camera tube, for example, by means ofa separate pickup light or in connection with film transmission bydetermining the average density of the film to be scanned just prior tothe time when it is. scanned and then introducing this direct currentcomponent into the video amplifier and the blacklevel control, abovereferred to, or by introducing the control directly into the modulator.In connection with film transmission, due to the rapidity with which thefilm moves, the control of the background is usually introducedautomatically by feeding the output from the photoelectric means whichcovers the average density of a film frame, as disclosed by Beverage,for example, through a D. C. amplifier and obtaining this direct currentcomponent from the film to be scanned at a number of frames prior to theac tual scanning corresponding substantially to the lag period of the D.C. amplifier. In connection with studio transmission, however, the D. C.component may be introduced by virtue of a manual control operated inaccordance with the actual view seen on a monitor of the transmittedimage, or the control of the background may be in accordance withmethods already described by Holmes, for exmaple, in United StatesPatent 112,109,618, granted. March 1, 1938.

Accordingly, in the system herein shown the system is of general utilityand applicable to studio pick-up, outdoor pick-up or motion picture filmpick-up of the view of which the image is to be reproduced at points ofreception. By the drawings there has been conventionally illustrated apick-up device or a camera I wherein is incorporated either a storagetype cathode ray type scanning tube 2 of the general nature shown byZworykin or a non-storage type tube of well known character. This tubeis for the purpose of providing a light image translation means and toaccomplish this objective there is directed up on the mosaic electrodeof this tube the view or subject for transmission. The view or lightimage is focussed upon the light resistive electrode of the scanningtube by a suitable form of optical means 3. Scanning deflection meansfor causing scanning action within the tube in well known manner, andwhich may comprise either electromagnetic or electrostatic means, or acombination of both, have been shown only schematically by the coils 5and I for the purpose of simplicity because the detailed arrangementsthereof are well known in the art. Likewise, connections to control thedevelopment and blanking during return line periods of the scanning beamwhich is developed within the neck portion of the tube have been omittedsince such controls are well known in the art and, per se, form no partof the present invention. The output energy from the scanning tube 2 isfed from the signal plate 9 of the mosaic electrode I l to a videopre-amplifier l3 and through other suitable amplifiers (not specificallyshown herein) wherein the shading adjustments which compensate for theso-called dark spot condition, for example, have been introduced andthence through any desired number of additional video frequencyamplifiers (not shown) to the modulator l5 wherein the carrier frequencydeveloped by the oscillator I1 is modulated and the resultant modulatedcarrier carrying only the video modulation is transmitted from theantenna [9.

Similarly the sound end of the system sound signal energy is picked upin a suitable form of sound pick-up or microphone device 25 and fedthrough a sound amplifier 21 to a modulator 29 wherein the radiofrequency carrier energy developed from the oscillator 31 is modulatedand the resultant signal is transmitted from the antenna 33. Theoscillators for the sound and the video signal carrier frequencies arespaced apart by fixed frequency separations, as disclosed by the Carlsonpatent above mentioned, for example, for the purpose of maintaining asubstantially constant spectral separation of the desired frequency bandwidth between the audio and the video carriers.

The line synchronizing generator 31 and the frame synchronizinggenerator 39 which control the deflection of the cathode ray beam of thescanning tube 2 are suitably interlocked with a synchronizing signalgenerator and the source of A. C. power supply (not shown) wherenecessary. The output energy developed by each of these generators 31and 39 is fed respectively to modulate in two oscillator modulatordevices 41 and 49 the super-audible frequencies developed from theoscillator portion of each. Similarly, the background control signalsource whose output signal indicates the general picture level orbrightness which is to be produced at the receiver is suitably amplifiedand caused to modulate in the oscillator modulator combination 55 thesuper-audible or sub-audible subcarrier frequency energy developed bythe oscillator portion thereof. The output from the severaloscillator-modulator devices 41, 49 and 55 wherein the super-audiblesub-carrier frequencies are modulated respectively by the linesynchronizing signal and the frame synchronizing signal, as well as thesuper or sub-audible frequency are fed to the combined modulator 29 forthe sound, the line synchronizing signal, the frame synchronizing signaland the background control signal. This resultant signal energy is thentransmitted from the antenna 33 to accompany the video transmission sentout from th television antenna l9.

Fig. 3 represents schematically the manner in which these severalsignals distribute themselves in the ether and on Fig. 4 the abscissaseparation indicates schematically relative frequency separationsbetween the sevenal carrier frequencies which are each identified bysuitable legends.

By Fig, 3 the spectral space required for the transmission of each ofthe signals has been conventionally shown, although it is to beunderstood that the lower side bands representing the backgroundcontrol, the frame synchronizing control and the line synchronizingcontrol have been omitted both for the sake of clearness of illustrationand for the reason that in practice it is usually unnecessary totransmit both the upper and lower side bands for these controllingsignals which are grouped on either side of the audio carrier. Asindicated schematically by Fig. 3, the sound signal carrier 62 is alsomodulated by three separate sub-carriers 63a, 64a and 65a which are, inturn, modulated by the background control signals 4|, the framesynchronizing control signals 42 and the line synchronizing controlsignals 43. It should be understood, however, that this sound carrier ismodulated by the audio signal 4!! as well. In this way, as shown by Fig.3, the frequency increase is in the direction looking from left to rightand while the side bands occupied by the modulation of the video carrierhave been shown as extending from a maximum to zero, it is, of course,obvious that zero video frequency need not be transmitted unless desiredbecause of the fact that a separate signal is provided for controllingbackground, Further, it should be understood that the contour of theside bands shown as grouped around each of the carriers and sub-carriersreferred to is purely schematic and in no sense intended to representthe energy distribution but rather must be considered as representativeof the frequency band actually or effectively occupied for thetransmission, and this is particularly true with respect to thebackground control where, from what will be pointed out herein infurther detail, the band width required for control is relatively narrowcompared even with the frame frequency.

It will be seen from an examination of the schematic representation ofFig. 3 that the video carrier is modulated by the video signals so thatthe side bands resulting extendfor an appreciable distance in thefrequency spectrum either side of the carrier. Where desired one ofthese side bands may be suppressed or both side bands may besimultaneously transmitted. As indicated on Fig. '3 a substantiallyfixed spectral separation FS is maintained between the audio ortelephone carrier and the video or television carrier. About the audiocarrier the super or sub-audible sub-carrier frequencies for the linesynchronizing signals, the frame synchronizing signals and thebackground control signals are grouped as conventionally illustrated,and the transmission of all of these are physically associated.

Referring now for a further understanding of the invention to Fig. 4,this figure also illustrates schematically substantially the samearrangement as shown by Fig. 3 with the background signal, however,serving to modulate a subaudible sub-carrier which in turn modulates thesound or telephone carrier, It can be appreciated that it is easilypossible and proper to modulate a sub-audible sub-carrier by thebackground signal since the frequency of such a signal is extremely low,due to the fact that background values of the subject for transmissiondo not change by appreciable amounts instantaneously or from one momentto another. As shown by Fig. 4 symmetrical side bands for both the framesynchronizing and the line synchronizing signals extend either side ofthe super-audible sub-carrier frequencies which modulate the soundcarrier and it is, of course, Within the scope of this disclosure towholly or partially eliminate either of these symmetrical side bands, asis the case with video side bands.

The arrangement of Fig. 5 illustrates schematically inexpanded form thegeneral relationship between the sound side bands actually grouped aboutthe sound carrier and the side bands resulting from backgroundmodulation (omitting herein any synchronizing control signals) where thebackground modulation is placed upon a subaudible sub-carrier which inturn modulates the sound carrier.

Fig, 6 illustrates a still further alternative where the backgroundsignal modulates the sound carrier directly and sub-audibly. Inconnection with the modulation which results'from the frame and linesynchronizing signals it will, of course, be appreciated that these sidebands, in general, extend for the frame synchronizing signalsapproximately cycles either side 'of the frame synchronizing modulatedintermediate frequency carrier and that the side bands, due to the linefrequency modulation, extend for a distancevof slightly more than 13kilocycles either side of the line synchronizing signal modulatedintermediate frequency carrier, assuming of course, that thetransmission i concerned with a 441 line picture interlaced at 30repetitions per second with a field frequency of 60 which is the form onwhich the greater portion of the experimental transmissions in thiscountry have been carried forward.

In the receiver end of the system, as shown by Fig. 2, the signalstransmitted upon the two separate audio and video carrier frequencies,and which include, on the one hand, the video signals and, on the otherhand, the audio signals and all or substantially all control signals forthe video, are received upon any suitable receiving antenna system 6|usually a di-pole, as is known in the art. The received signals(combining video :andgaudio as well as the control signals) are directedthrough suitable selector circuits E3 and if desirable amplifiers into acommon receiver and heterodyne detector circuit to which the frequencyoutput of the local oscillator 61 is supplied. As was disclosed by theabove,

mentioned Carlson patent, it is possible, in view of the substantiallyfixed separation between .the video and the audio carrier frequencies totune the receiver to the sound signal only in order to receive both theaudio and the video signals properly selected, The output from thereceiver and detector 65 which is signal energy at the desiredintermediate frequencies is then fed through filters to separate thevideo intermediate frequency from the audio intermediate frequencyresulting upon detection by detector 65, as well as the auxiliarysignals accompanying the audio signal. In practice, it has beencustomary to transmit the audio signals on a higher carrier frequencythan the video and, therefore, the selection and separation of the videointermediate frequencies is preferably taken care of by a low passfilter 61, while the audio intermediate frequencies and the accompanyingcontrol signals for controlling the video end of the system areseparated by way of a high pass filter 69.

In the video end of the system as is the usual custom the output signalsfrom the low pass filter 61 are fed through an intermediate frequencyamplifier 1| and a detector 13 to the image reproducing tube 15. For theaudio signals the output of the high pass filter 69 is amplified in theintermediate frequency amplifier 11 and then detected by detector 19. Inview of the fact that the control signals for the video end of thesystem accompany the audio signals there is connected to the output ofthe audio intermediate frequency detector 19 a high pass filter 8| whichseparates from the composite intermediate frequency energy output of thedetector 19 the complete group of signals representing the linesynchronizing signal energy. These signals are then detected in aheterodyne detector 83 to the input of which is applied the output fromthe oscillator 85 and after suitably controlling the synchronizingsignal and deflecting circuit control arrangement 81, of the type knownin the art and described, for example, by Tolson, Bedford and Vance andothers, is caused to deflect the cathode ray beam developed within thecathode ray receiver tube and also caused where necessary or desirableto produce blanking in the receiver tube.

Similarly, by way of a bandpass filter selection means 89 whose outputis fed to the heterodyne detector 9| the frame synchronizing signals areseparated and these signals then serve to control the deflection of thecathode ray beam in a manner closely analogous to the line deflection sothat the cathode ray beam of the receiver tube 15 is deflecting in thevertical direction. Kny background control signals which are transmittedto accommpany the audio carrier are separated by way of the low passfilter 93 which preferably has a cut-off frequency at approximately tocycles. Thence the separated background control signals are impressedupon the input of the heterodyne detector 95 and amplifier 91 so thatthe output from this amplifier serves to bias in known manner thecontrol elec trode of the image reproducing tube 15.

It will be noted that by virtue of the fact that the low pass filter 93has a cut-off at sub-audible frequency of approximately 20 to 25 cyclesthat this serves also the additional purpose of limiting the'rate ofchange of field brightness in the receiver so that on conditions whenthe transmission scene changes from a very bright picture to a darkportion the abruptness of the change will not be objectionably apparentbut will be integrated slightly over a short period of time In this waysubstantially the effect of a gradual changing background effect can beobtained.

The audio signals, like the frame synchonizing signals, are preferablyselected in a bandpass filter 94 which selects from the lowestaudio-frequency of about 30 cycles up to the frequency corresponding tothe maximum fidelity of the system, which is usually a frequency ofabout 10 kc., and the audio signals are then detected in the heterodynedetector 95 and further amplified in the amplifier 96 and then suppliedto the sound reproducer 99.

Since all the foregoing individual sections of the complete apparatusare substantially of standard form reference is made to the prior artand particularly to the form of installation now being usedexperimentally in the United States for a complete description of theindividual units of the receiver as well as the transmitter.

It should be appreciated also that while the schematic diagram of thereceiver system does not show automatic volume control arrangements,such arrangements are fully Within the scope of this disclosure and forthis portion of the system, like other portions, reference also may behad to the aforementioned Carlson patent.

Many and various modifications of the system herein disclosed are,naturally, possible and within the scope of this disclosure and it is tobe understood that I am free to make and use any and all of thesemodifications provided they fall fairly within the spirit and scope ofthe hereinafter appended claims.

What I claim is:

1. In a television system, means for producing carrier frequency energy,means for developing video signals and means for modulating the producedcarrier frequency energy by the developed video signals, means forproducing a plurality of controlling signals for controlling thereproduction of the produced video signals at all points of reception,means for producing sound signals accompanying the produced videosignals, means for producing a second carrier frequency having apredetermined frequency spacing from the first produced carrierfrequency energy, means for producing auxiliary sub-carrier frequenciesof a number corresponding to the number of auxiliary controlling signalsproduced for controlling the reproduction of video signals at receptionpoints therefor, means for modulating each of the produced auxiliarysub-carrier frequencies by individual controlling signals, and means formodulating the second produced carrier frequency by both the soundsignals and the control signal modulated auxiliary submarrierfrequencies.

2. In a television system wherein video signals are transmitted upon onecarrier frequency and wherein sound signals accompanying the videosignals and the control signals for the video reproduction areconcomitantly transmitted upon a separate carrier frequency spaced by apredetermined frequency separation from the video carrier, a signalreceiving means for receiving all of the transmitted signals, a commonheterodyne detecting means for detecting all of the received signals andconverting all of the received signals into intermediate frequencysignals, means for separating the produced video modulated intermediatefrequency signals from the produced sound modulated intermediatefrequency signals and the video control signal modulated intermediatefrequency signals accompanying the sound, means for amplifying the videomodulated intermediate frequency signals subsequent to separation fromthe remaining received signals, means for detecting the amplified videomodulated intermediate frequency signals, means to produce visiblesignal indications from the resultant detected video signals, means foramplifying the separated intermediate frequencies modulated by the soundand the video control signals, means for detecting said last namedamplified signals, a plurality of filter means for separating the soundand the video control signals from each other, and independent means forconverting the separated sound signals into audible signals and forcontrolling the production of the video signals in accordance with theseparated video control signals.

3. In a television system wherein video signals are transmitted upon onecarrier frequency and sound signals accompanying the video signals and aplurality of control signals for the video reproduction are eachtransmitted upon a separate carrier frequency spaced by a predeterminedfrequency separation from the video carrier, a single receiving meansfor receiving all of the transmitted signals, a common heterodynedetecting means for detecting all of the received signals and forconverting all of the received signals into signals occupying anintermediate frequency range, means for separating the video modulatedintermediate frequency signals from the intermediate frequency signalsmodulated by the sound signals and the video control signals, means foramplifying the video modulated intermediate frequency signals subsequentto the separation thereof from the remaining signals, means fordetecting the amplified video modulated intermediate frequency signals,means to produce visible signal indications from the resultant detectedvideo signals, a plurality of separating circuits for separating thesound modulated intermediate frequency signals and the video controlsignal modulated intermediate frequency signals, means for detectingsaid separated sound signals, means comprising a plurality of filtersfor separating the plurality of video control signals from each other,means for converting the separated sound signals into audible signalsand means for controlling the production of the video signals inaccordance with the separated video control signals.

4. In a television system means for producing a first main carrierfrequency energy, means for developing video signals and means formodulating the produced carrier frequency energy by the developed videosignals, means for producing controlling signals for controlling thereproduction of the produced video signals at all points of reception,means for producing signals representative of the sound accompanying theproduced video signals, means for developing a second main carrierfrequency spaced by a predetermined frequency spacing from the firstproduced carrier frequency, means for producing auxiliary sub-carrierfrequencies of a number corresponding to the number of auxiliary controlsignals produced for controlling the reproduction of the video signalsat reception points, means for independently modulating each of theproduced auxiliary sub-carrier frequencies by individual controllingsignals, means for developing background control frequencies at asub-audible rate for controlling the video signal reproduction levels,and means for modulating the second produced main carrier frequencydirectly by the produced sound and background control signals and by thepreviously modulated auxiliary sub-carrier frequencies for transmittingthe second produced main carrier frequency modulation simultaneouslywith the first produced main carrier frequency modulation.

5. In a television system, means for producing a first main carrierfrequency, means for develop-' ing video signals, means for modulatingsaid produced first main carrier frequency by the developed videosignals, means for developing a second main carrier frequency spaced ata predetermined frequency separation from the first main carrierfrequency, means for developing signals representative of the soundaccompanying the produced video signals, means for modulating the secondproduced main carrier frequency directly by the produced sound signals,means for producing a plurality of separate synchronizing signals forcontrolling the reproduction of the produced video signals at points ofreception, means for developing a background control signal forcontrolling the reproduction of the produced video signals at points ofreception, means for producing a plurality of auxiliary sub-carrierfrequencies of a number corresponding to the number of developedsynchronizing signals and background control signals, each of saidauxiliary subcarrier frequencies being of different frequency and eachbeing of a frequency sufiiciently different from that of the maximumside-band frequency developed by the sound signal modulation of thesecond main carrier frequency as to be external to the frequencyspectrum developed by sound signal modulation of the second main carrierfrequency, and each of said auxiliary subcarrier frequencies beingspaced apart from all other auxiliary sub-carrier frequencies by afrequency separation such that the frequency spectra of auxiliarysub-carriers and generated sidebands resulting from modulation of thesaid auxiliary sub-carrier frequencies shall be noncontiguous, means forindependently modulating a number of the auxiliary sub-carrierfrequencies equal to the number of independent synchronizing signalsindividually by individual ones of said produced synchronizing signals,means for modulating one of the auxiliary sub-carrier frequencies 'bythe produced background control signals only, and means for modulatingthe second produced main carrier frequencies by the plurality ofmodulated auxiliary sub-carrier frequencies.

ALFRED N. GOLDSMITH.

